This invention relates generally to drug infusion devices and, more particularly, to drug infusion devices driven by electrochemical pumps.
A variety of types of drug infusion devices are used to dispense drugs to a patient continuously over a period of many hours. Such devices include gravity dispensers, mechanical pump dispensers, pressurized gas dispensers and osmotic pressure dispensers. A gravity dispenser utilizes the force of gravity to dispense a drug from the familiar plasma bottle suspended above the patient. A mechanical pump dispenser generally includes some type of electrically-driven mechanical pump, while a pressurized gas dispenser utilizes a tank of some suitable pressurized gas to dispense the drug. An osmotic pressure dispenser relies on a solute that exhibits an osmotic pressure gradient against water to dispense the drug.
However, when small quantities of drugs, such as hormones, must be administered continuously over a period of many hours, a drug dispenser that is highly accurate, yet small enough to be portable, that can be miniaturized and therefore implanted, and that has no moving parts is preferred. None of the above-mentioned types of drug dispensers can meet all of these requirements. A copending patent application filed by one of the present joint inventors, entitled ELECTROCHEMICALLY DRIVEN DRUG DISPENSER, Ser. No. 729,860, discloses an electrochemically driven drug dispenser that does meet all of these requirements. The electrochemically driven drug dispenser includes an electrochemical pump that operates as a variable pressure source and provides highly accurate control of the delivery rate of these small quantities of drugs.
Although the electrochemically driven drug dispenser disclosed in the above-mentioned patent application has many advantages, it operates in a constant delivery mode and is not easily adapted to deliver drugs in a pulsatile or peristaltic delivery mode. Pulsatile or peristaltic drug delivery duplicates the body's natural delivery of, for example, certain types of hormones. Accordingly, there has been a need for a drug dispenser which is portable, can be miniaturized and therefore implanted, is highly accurate in the delivery of small quantities of drugs, and can deliver drugs with a pulsatile or peristaltic motion.